This isn't as creative as Instructables usually are, but I now have three toilet planters. AND I LOVE THEM! trailing plants like ivy or petunias look really pretty in the water tanks, and hosta's, succulents and other plants have done really well in the bowls.
I love these planters because they are a little silly and LOT unique, and they didn't get put in the landfill!
I put quarter sized landscape rocks in the bottom for drainage and then planted as usual! I don't have an HOA, so I didn't have to worry about them as some people might.
Also of note, I work at a theatre and we bought new toilets, but the habitat restore wouldn't take them after the shows closed, as they were technically used, so this was a good way to upcycle!
1 used toilet
2-3 lbs of white gravel
one medium sized bag planting soil